The invention relates to optical codes, e.g., DataMatrix bar codes and to making them more secure and easier to be detected and read. The invention greatly simplifies the detection of the machine-readable symbology for reading by a bar code reader.
Optical codes are used in a wide variety of contexts, including product packaging, mail sorting, and inventory control, among others. Optical codes take the form of visible or machine-readable patterns made up of image areas having different light reflective or light emissive properties which conform to defined rules. A “bar code” is a type optical code, and typically comprises a printed pattern of geometrical shapes in one-dimensional or two-dimensional patterns.
Among frequently employed optical codes are those based on two-dimensional grids, having a geometry independent of data content. The grid may be a plane tiled by regular polygons such as squares or hexagons. Typically, a black or white feature or polygon is located at each grid location.
DataMatrix bar codes are a form of optical codes used for many data intensive applications and often find security a desired feature. Because they depend on machine reading, it is important to provide a pattern and printing method that assure proper recognition and accurate reading at high throughputs. There is a present need for systems that can provide enhanced security and/or readability.
The optical properties and patterns of optical codes are selected to distinguish them in appearance (or machine readability) from the background environments in which they are used. Devices for identifying or extracting data from optical codes are sometimes referred to as “optical code readers” of which DataMatrix bar code scanners are one type, and they are used in both fixed and portable installations. An optical code should be easily recognized and rapidly read to provide rapid data entry for data base generation or real-time operation of article manipulating equipment, e.g., sorters. To assure rapid pattern recognition and accuracy of reading the codes, optical code readers are typically provided with a target code and connected to data processing device or a data collection and transmission device.
A DataMatrix barcode typically comprises a two-dimensional matrix symbology made up of nominally square modules arranged within a perimeter finder (target) pattern. The perimeter will be distinctive in geometry to permit easy detection, discrimination from background printing or other markings, and reading for location and orientation. Though primarily shown and described as a dark symbol on light background, DataMatrix symbols can also be printed to appear as light on dark. The symbols can be read or made recognizable by light reflectance or by fluorescence by selection of the appropriate ink.
Manufacturers of optical code printing and reading equipment and users of the technology require publicly available standard symbology specifications to which they can refer when developing equipment and application standards. The publication of standardised symbology specifications is designed to achieve this. In all cases, the images should be easily recognized by machine reading equipment and should enable rapid reading with high accuracy. It would be desirable to have an improved system that could utilize standard equipment for printing and reading and could also take advantage of equipment improvements to enhance security and/or readability.
DataMatrix bar codes comprise one particularly useful form of optical code and are typically provided with enhanced readability by the use of a distinctive perimeter pattern which provides a target area around a DataMatrix pattern including the principal data source. Due to any number of factors involved with printing and subsequent handling, the signal to noise ratio in the environment of other visible, monochrome printing is often problematic when printed with monochromatic inks for reflective reading with light in the visible range.
One of the most time consuming (or data processing intensive) parts of reading a barcode or other machine-readable symbology is detecting the symbol. This portion of the reading process must be complete and assured accurate before the data within the DataMatrix can be read and analyzed for many applications. There is a real need to simplify the symbol detection process and to assure that the data is being read properly.
A further problem with the art is identifying simple copies of an original barcode. Simple copies are any copies produced by a scanner and office printer or by a photocopier. In the context of tickets, postage and the like, there is often a need to read these bar codes with small hand held equipment for verification and there is a great need for simplicity and accuracy. There is a real need to assure that the data is being read from an authorized document and not a simple copy.
Security is important in many contexts, and the art has provided a number of inks for making documents more secure. For example in U.S. Pat. No. 6,835,326 to Barbera-Guillem there is described a fluorescent ink composition comprising functionalized fluorescent nanocrystals. In another approach described in U.S. Pat. No. 6,770,687 to Tan, et al., a water-based security printing ink is provided with two means of security. The use of a variable light absorbing and/or transmitting pigment or dye is a first security and a water repelling agent is provided as a second security. Visible images can be generated from the printed ink upon exposure to UV or infrared light. The water repelling agent renders the image waterproof and differentiates the printed image from the substrate, which allows the image to be detected upon exposure to water or other aqueous mixture.
Black fluorescent inks have also been described as having a desirable security feature. Among these are as photosensitive optically variable inks, a term used to define inks that can provide printed visually black or dark grey machine-readable information-bearing markings that fluoresce in a specific wavelength range when excited with a shorter wavelength light. The printed images exhibit visual light absorption throughout the entire visual spectrum including the red region of the visible spectrum where red inks are invisible to typical automatic scanning systems. Inks representative of this type are described, for example in U.S. Pat. No. 6,793,723 to Auslander, et al., entitled Homogeneous Photosensitive Optically Variable Ink Compositions For Ink Jet Printing and U.S. Pat. No. 6,827,769, also to Auslander, et al., and entitled Photosensitive Optically Variable Ink Heterogeneous Compositions For Ink Jet Printing. It would be desirable to have processes that can take advantage of inks possessing unique security features in ways that can enhance the detection and/or security of optical codes such as DataMatrix and other bar codes.
There is a need in the art of optical codes, e.g., DataMatrix bar codes, printing and processing to simplify the symbol detection process for postal and other purposes and also to enable identification of simple copies of an original barcode or other optical code, both to be enabled for automatic equipment for verification with simplicity and accuracy.